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Liu X.,North China University of Technology | Ma S.,China Longyuan Power Group
2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 | Year: 2015

In the DC power systems of More Electric Aircraft, the closed-loop controlled electrical motor drives and power electronic converters can be generally regarded as constant power loads (CPLs), and usually lead to negative impedance-related instability. Depending on Brayton-Moser's mixed potential theory, this paper adopts R parallel damping filters to stabilize the CPLs systems, and derives large signal stability criteria. The simple criteria utilize the dynamic negative impedance of the CPLs to place quantitative constraints on the filter parameters, and provide important design guidelines during the filter determination. Comparisons demonstrate the stability criterion for the CPLs with a single-stage LC filter can be regarded as a special case of the proposed criteria. The region of asymptotic stability (RAS) around the stable equilibrium point is obtained, and it indicates the criteria can guarantee the system stability during large disturbances. The experimental results also confirm the validity of the proposed stabilization method. © 2015 IEEE.

Wang X.,Tsinghua University | Ren H.,Tsinghua University | Ren H.,China Longyuan Power Group | Wu B.,CSIRO | And 2 more authors.
Acta Mechanica Solida Sinica | Year: 2014

Fatigue cracking tests of a solder joint were carried out using in-situ scanning electron microscopy (SEM) technology under tensile and bending cyclic loadings. The method for predicting the fatigue life is provided based on the fatigue crack growth rate of the solder joint. The results show that the effect of the loading type on the fatigue crack growth behavior of a solder joint cannot be ignored. In addition, the finite element analysis results help quantitatively estimate the response relationship between solder joint structures. The fatigue crack initiation life of a solder joint is in good agreement with the fatigue life (N50%) of a totally electronic board with 36 solder joints. © 2014 The Chinese Society of Theoretical and Applied Mechanics.

Long H.,City University of Hong Kong | Wang L.,City University of Hong Kong | Zhang Z.,City University of Hong Kong | Song Z.,Nanjing University | Xu J.,China Longyuan Power Group
IEEE Transactions on Industrial Electronics | Year: 2015

This paper investigates the wind turbine power generation performance monitoring based on supervisory control and data acquisition (SCADA) data. The proposed approach identifies turbines with weakened power generation performance through assessing the wind power curve profiles. Profiles that statistically summarize the curvatures and shapes of a wind power curve over consecutive time intervals are constructed by fitting power curve models into SCADA data sets with a least square method. To monitor the variations of wind power curve profiles over time, multivariate and residual approaches are introduced and applied. Two blind industrial studies are conducted to validate the effectiveness of the proposed monitoring approach, and the results demonstrate high accuracy in detecting the abnormal power curve profiles of wind turbines and their associated time intervals. © 2015 IEEE.

Yong Z.,China Longyuan Power Group | Wei D.,Beijing Longyuan wind power engineering consultation company
European Wind Energy Conference and Exhibition, EWEC 2013 | Year: 2013

With the emergence of grid connection issue and wind power production curtailment,wind power storage is drawing more attentions. The conventional energy storage like battery cannot be applied commercially due to high cost and technological immaturity. Thermal energy storage can be used in wind power application as that electricity from wind power is converted into thermal energy which is then converted into electricity through steam turbine generator. To increase efficiency, combined heat and power generation is used in this application, which is more valuable in the areas as Northeast China and Inner Mongolia. These places are feathered by high wind speed, high heat demands and severe wind power output curtailment.

Li M.,Gansu Electric Power Company | Tang X.,China Longyuan Power Group | Dan Y.,Zhejiang Electrical Power Test and Research Institute | Cai W.,North China Electrical Power University | Liu W.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2015

Large-scale grid-connected wind power greatly changes power grid network structure and power flow distribution, especially, fluctuations of wind power directly aggravates power grid's tendency to self-organization critical state, and cascading grid failure risk also increases. After deeply analyzing influence of large-scale grid-connected wind power on self-organized criticality evolution process of power grid, wind power fluctuations entropy is proposed to characterize effect of large-scale grid-connected wind power on self-organized criticality evolution of power grid. Simulation analysis proves that the proposed entropy can well characterize effect of large-scale grid-connected wind power on self-organized criticality evolution of power grid, and can be used as one of physical indicators of grid self-organized critical state identification with large scale wind power. © 2015, Power System Technology Press. All right reserved.

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